The present invention relates generally to a magnetic tape cassette, such as a cassette specifically adapted for pulse-code modulated (PCM) recording and/or reproduction. More specifically, the invention relates to a tape protective structure for a magnetic tape cassette for protecting a magnetic tape when the magnetic tape cassette is not in use.
In recent years, various recording and/or reproducing apparatus have been developed which convert analog signals, such as audio signals and the like into digital signals, e.g. PCM signals, which are then recorded on and reproduced from magnetic tape serving as a recording medium. Some of these apparatus employ rotary heads in order to achieve a relatively high recording density. Recording and/or reproducing apparatus specifically designed to record and reproduce PCM signals and employing a rotary head will be referred to as "PCM recorders" throughout the disclosure. A PCM recorder, at first, pulls a loop of magnetic tape out through a front opening of the cassette and winds the tape around a rotary drum accommodating the rotary head and then the recording and reproducing is performed. In such digital recording and reproducing systems, oily deposits, such as fingerprints or the like, and/or dust adhering to the tape surface may cause dropout of reproduced signals.
Various approaches have been tried to protect the magnetic recording medium. For example, the European Patent First Publication No. 01 60 822, published Nov. 13, 1985, and the British Patent First Publication No. 2,155,905, published Oct. 2, 1985, which respectively disclose prior inventions commonly owned by the owner of the present invention, disclose magnetic tape cassettes which respectively have closure lids for retractably covering the front end openings of the cassettes, through which the tape is extracted for access by rotary heads. Each such closure lid is held closed while the tape is not in use and is moved to an open position when the cassette is inserted into the PCM recorder. In this earlier approach, a drawback may be encountered when the closure lid is unintentionally or accidentally opened, exposing the tape to oily fingerprints, dust and so forth while it is not in use. A locking mechanism which can conveniently lock the closure lid in its open and closed positions could resolve this problem.
The magnetic tape cassette disclosed in the aforementioned the European Patent First Publication No. 01 60 822 and the British Patent First Publication No. 2,155,905 also has a sliding closure for closing a lower openings which allow entry of a loading device and tape reel drive of the recording and reproducing apparatus. The sliding closure may also be movable between open and closed positions. The sliding closure may be associated with a lock mechanism for locking the sliding closure at least in its closed position. The lock mechanism may be released by a mechanism or device provided in the recording and/or reproducing apparatus for releasing the locking mechanism from a locking position so that the closure may move between open and closed positions.
The present invention is directed to an improvement in the prior proposed sliding closure locking mechanism for magnetic tape cassettes of the type disclosed in the European Patent First Publication 01 60 822 and the British Patent First Publication No. 2,155,905.